Blender - solve this shading difference?
Those look like two entirely separate objects with geometry overlapping. There is no way to fix non-continuous shading between different objects except for overly-elaborate normal maps. If they're part of the same object, hover over one mesh and press L in edit mode. If only whichever part of the body you've hovered over lights up orange (it's then selected), that means you can't fix it until all of the vertex points where the meshes intersect are joined, at which point you'll be able to smooth the normals.